Merge pull request #244 from JuliaSymbolics/myb/sign

Eagerly evaluate registered function if arguments are not symbolic

src/extra_functions.jl

@@ -2,9 +2,9 @@
 @register Base.getindex(x,i) # define one and only one promotion rule
 @register Base.binomial(n,k)
 
-Base.sign(x::Symbolic) = Term{Int}(sign, [x])
-Base.sign(x::Num) = Num(sign(value(x)))
+@register Base.sign(x)::Int
 derivative(::typeof(sign), args::NTuple{1,Any}, ::Val{1}) = 0
+
 @register Base.signbit(x)::Bool
 derivative(::typeof(signbit), args::NTuple{1,Any}, ::Val{1}) = 0
 derivative(::typeof(abs), args::NTuple{1,Any}, ::Val{1}) = IfElse.ifelse(signbit(args[1]),-one(args[1]),one(args[1]))

src/register.jl

@@ -1,3 +1,4 @@
+using SymbolicUtils: Symbolic
 """
     @register(expr, define_promotion = true, Ts = [Num, Symbolic, Real])
 
@@ -50,7 +51,12 @@ macro register(expr, define_promotion = true, Ts = [Num, Symbolic, Real])
         push!(ex.args, quote
             function $f($(setinds(args, symbolic_args, ts)...))
                 wrap =  any(x->typeof(x) <: $Num, tuple($(setinds(args, symbolic_args, ts)...),)) ? $Num : $identity
-                wrap($Term{$ret_type}($f, [$(map(name, args)...)]))
+                args = ($(map(name, args)...),)
+                if all(arg -> !(arg isa $Symbolic), args)
+                    wrap($f(args...,))
+                else
+                    wrap($Term{$ret_type}($f, collect(args)))
+                end
             end
         end)
     end

test/overloads.jl

@@ -168,7 +168,8 @@ eqs = [
 @test [2 1 -1; -3 1 -1; 0 1 -5] * Symbolics.solve_for(eqs, [x, y, z]) == [2; -2; -2]
 @test isequal(Symbolics.solve_for(2//1*x + y - 2//1*z ~ 9//1*x, 1//1*x), 1//7*y - 2//7*z)
 
-@test isequal(sign(x), Num(SymbolicUtils.Term{Int}(sign, [x])))
+@test isequal(sign(x), Num(SymbolicUtils.Term{Int}(sign, [Symbolics.value(x)])))
+@test sign(Num(1)) isa Num
 @test isequal(sign(Num(1)), Num(1))
 @test isequal(sign(Num(-1)), Num(-1))